The manufacturing industry, and in particular the metal fabrication and stamping industries, commonly utilize automated systems that allow a workpiece to be conveyed or transferred between equally spaced workstations where particular operations are carried out upon the workpiece. For example, many metal parts on automobiles and appliances are formed by means of a stamping procedure wherein a series of separate dies are situated on a series of aligned and equally spaced workstations within a press bed such that a workpiece will be stamped between a pair of dies upon each stroke of the press. Automated transfer systems are typically employed to grasp the workpiece, remove it from one set of dies, and transport it laterally through the press bed to the next adjacent workstation where the workpiece will be stamped a second time with a further set of dies upon the next stroke of the press.
A press transfer system utilized in conjunction with a typical multi-stage press would commonly include at least one transversely oriented transfer rail situated adjacent to the press bed and aligned with the various workstations. Depending upon the particular application and press design, a single transfer rail may be positioned along one side of the press bed or, alternatively, a separate transfer rail may be located on each side of the bed of the press. Regardless, the primary function of the transfer rail is to provide a mechanism by which grippers or fingers may be supported adjacent to the workstations for grasping a workpiece so that it may be transported to the next workstation. Such grippers or fingers would typically be mounted either to the transfer rail or to a secondary rail that is in some manner secured or attached to the transfer rail. Movement of the workpieces from workstation to workstation accordingly involves the movement of the transfer rail, often in a relatively complex three dimensional manner. Described generally, this movement involves (i) moving the rail toward the workstation such that the grippers may grasp the workpiece; (ii) lifting upwardly to remove the workpiece from the dies in the workstation; (iii) moving laterally and parallel to the press bed to align the workpiece with the next adjacent workstation; (iv) lowering to allow the grippers to release the workpiece onto the next adjacent set of dies; and, (v) retracting from the workstation and returning back to the starting position.
It will therefore be appreciated that to present an effective mechanism by which a workpiece may be moved in the above-described fashion, the transfer rails must be relatively rigid, must be of a sufficient strength to support workpieces without significant flexure or deflection from the horizontal, and preferably of a relatively light weight construction so as to minimize the inertia of the moving transfer rails to permit more precise and faster movement of workpieces between workstations.
It is common in metal fabrication and stamping facilities for one press to be used in the manufacturing of a variety of different components. Changing the set up of a press to enable the stamping of different components usually necessitates the removal and change-out of the dies. It may also be necessary for the press operator to change or modify the grippers or fingers to accommodate a new workpiece. Changing the dies within the press bed typically requires the transfer rails to be removed from the transfer system to allow for complete and open access to the dies. In addition, changing grippers or fingers to accommodate a new size and shape of workpiece often requires the transfer rails be removed so that new grippers or fingers can be mounted thereon, or that a new transfer rail be installed that has already been pre-fitted with the necessary grippers. In either instance the physical removal of the transfer rail can be a laborious and time consuming procedure adding expense to the manufacturing process by way of increased operator time and by increasing the down time of the press.
To address the need to be able to easily and quickly remove transfer rails to gain access to the press bed, and to facilitate the change-out of grippers or fingers, others have manufactured transfer rails in a series of separate longitudinal sections fastened together at their ends to form a single elongate rail. Consecutive sections of the rail are typically fastened together through the use of bolts, plates or a variety of externally mounted mechanical, pneumatic or hydraulic latches and/or catches. Unfortunately, such transfer rails have generally met with limited success as the systems utilized to fasten rail sections together end to end have tended to be either no more convenient than simply removing the entire rail, or mechanically complex thereby making them more costly and more prone to failure. Furthermore, such prior connecting systems have tended to present a weakness in the structural integrity of the rail at the juncture of adjacent sections. To combat the potential weakness at the location where successive rails are connected, others have reverted to the use of bulky, heavy, high strength components that are capable of transferring load between rail sections without significant deflection or sag. Such components are typically undesirable on account of the increased weight that they add to the transfer rail.